In order to manufacture products comprised of tubular metal, such as automotive exhaust systems, roll-cages and numerous other framed support structures, it is necessary to join sections of hollow metal tubing by means of arc welding, electron beam welding, laser welding and brazing or soldering. In order to accomplish proper interconnection of such tubing members for permanent union it is first necessary to “notch” one of the tubes so that it matingly conforms to the exterior surface of the tube to which it is to be connected. Several methods have been employed to achieve the desired fit of such abutting tubular surfaces including the use of hand-held coping tools, punch and die combinations and band saws. The subject invention relates to yet another species of notching apparatus, namely a rotary cutting tool or “hole saw”.
Heretofore, a variety of rotary cutting devices have been designed to produce precisely contoured ends of tubing for connection with the periphery of another tubing member. Some such devices are hand-held while others are surface mounted. Of this latter type, some are designed to maintain the cutting tool in vertical orientation above the work piece, such as by mounting the device in a drill press or in a vice and attaching a hand drill. The orientation of the work piece relative to the cutting tool is then manipulated to achieve the proper angle of penetration. A first problem with this arrangement is that there is often insufficient room to properly position elongate tube members since movement is impeded by either the floor (when adjusting the tube about a vertical plane) or by surrounding walls or other table mounted equipment (when adjusting the tube about a horizontal plane). A second problem frequently encountered is that the weight of the hand drill causes the cutting member to descend too rapidly into the work piece which can result in binding and/or damage to the work piece.
In order to obviate the shortcomings and limitations of the above described prior art surface-mounted tube notching devices it has been found useful to achieve the desired angles of penetration by retaining the work piece in a fixed and preferably horizontal position while adjusting the orientation of the cutting tool relative thereto, rather than visa versa. One such device is described in U.S. Pat. No. 5,118,228 issued to Story in 1992. Story teaches that a length of steel tubing may be confined within a pipe support unit using clamping means and an articulated cutter head unit may then be aligned to intersect the midpoint of the steel tubing at a desired angle. The key here is that the work piece remains stationary and secure while the cutter head is disposed at a selected angular orientation relative to the work piece. The hand drill is then attached to the shaft of the cutter head to impart rotary motion. An apparent shortcoming of the Story device, is that the carriage unit which supports the cutter head unit is comprised of two relatively thin and elongated arms which are likely to bend under the weight of an attached hand drill thereby causing misalignment of the cutting head and pipe.
Moreover, tube notching devices of the prior art are neither designed for nor suited to create offset notches in the work piece (i.e., where the center of the hole saw does not intersect the longitudinal axis of the work piece) or to notch curved sections of bent tubing. In view of the shortcomings and limitations of the prior art there has existed a longstanding need for a rotary tube notching apparatus designed to securely holding both straight and bent tubing and having means for adjusting the orientation of the cutting mechanism about both a horizontal and vertical plane such that it may create straight, angled and offset notches in the work piece. The subject apparatus fulfils these objectives and others as set forth in greater detail herein.